1. Technical Field
The present invention relates to a retractable safety syringe and, more particularly, to a prefillable auto-retractable safety syringe including a retractable needle assembly and a collapsible plunger operable to facilitate the retraction of needle after the injection is completed.
2. Description of Related Art
Bloodborne diseases such as AIDS, hepatitis A, or hepatitis C, are transmitted through contact with blood or body substances. Bloodborne pathogens are known for transmitting serious or fatal diseases, and that the major transmitting route is an accidental needle-stick injury caused by inadvertent operation of a syringe, or inappropriate reuse of needles. An improper operation or disposal of syringes with exposed needles often leads to accidental needle-stick injury, and healthcare workers are thus easily exposed to bloodborne pathogens, and even hospital employees may be exposed to significant risk of contagion. Moreover, reusing an unsterilized or contaminated syringe may result in the spread of diseases, Unfortunately, reusing or sharing needles is significant among drug addicts, and unauthorized use of a syringe is commonly associated with a use of illegal drugs, that dramatically increases the risk of infection, and the consequent spread of those bloodborne diseases becomes a serious threat to public health.
In order to reduce the mentioned risks and the problems, non-reusable safety injection devices or syringes are nowadays widely used. Currently, safety syringes using a spring-based mechanism are the most common design for automatically retracting the needle after injecting. For example, U.S. Pat. No. 8,088,110 B2 entitled “AUTOMATICALLY RETRACTABLE SAFETY INJECTION DEVICE FOR NON-LIQUID MATERIAL” disclosed a safety syringe.
As shown in FIGS. 1A and 1B, a conventionally known safety syringe 9 has a cap 900, a needle hub 91 connecting a needle 90, a hollow barrel 92 connecting the needle hub 91, an annular spring 93 in a compressed state, and a collapsible plunger combination 94 settled in the hollow barrel 92. The collapsible plunger combination 94 includes a rod 941 with a plunger head 942, a retractable plunger 95 and a hollow plunger 96. The hollow barrel 92 is disposed with a plurality of elastic and slightly flexible retaining hook 922 at the front end thereof, while the needle hub 91 is formed with a plurality of slots 913, slopes 914, turning chutes 915 and guiding chutes 916. The retaining hooks 922 of the hollow barrel 92 engage with the slots 913 to clamp the needle hub 91 during the operation the safety syringe 9 until the injection of an injectant 97 is completed. The retaining hooks 922 start to be indirectly pressed and flexibly expanded to be disengaged with the slots 913 when the user continuously presses the hollow plunger 96 after the injection of the injectant 97 is completed, and the retaining hooks 922 consequently slides along the slopes 914, the turning chutes 915, and the guiding chutes 916 in an order to decompress the annular spring 93 so as to guide and push the needle hub 91 backward into the hollow barrel 92.
Regarding the disclosed syringe 9, it is noted that the disengagement of the retaining hooks 922 of the hollow barrel 92 with the slots enables the annular spring 93 not only to be decompressed but also to be rotated, and this rotation of the annular spring 93 is likely to impede the retraction of the needle hub 91 and therefore the needle hub 91 would not be completely retracted into the hollow barrel as good as desired or even fails to start the retraction. As a result, the whole retraction mechanism still has malfunction possibilities and become less reliable, and therefore causes the user to be under the mentioned threat.
However, these safety syringes by their nature have sophisticated design, increased number of parts, and consequently requires complicated fabrication procedures, which often leads to lower product yield rate and higher production costs. The higher cost of safety syringes, apart from the concern of functional reliability, is a major obstacle of marketing the advanced safety syringes.
Therefore, aiming at providing flawless protection against needle-stick injuries to healthcare workers to prevent from infection of potentially fatal bloodborne pathogens, an improved and safer design for a safety syringe is provided hereinafter.